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International Concrete Abstracts Portal

Showing 1-5 of 19 Abstracts search results

Document: 

SP75-04

Date: 

September 1, 1982

Author(s):

Jan Ove Holmen

Publication:

Symposium Papers

Volume:

75

Abstract:

In this investigation, the effect of various load histories on the fatigue behaviour of plain concrete was studied. (1). A total of 462 cylindrical specimens (100x250 mm) were tested statically and dynamically in compression. In addition, a total of 18 cylinders (150x300 mm) plus 132 cubes (100 mm) were tested statically. In addition to fatigue strength, special interest has been paid to the deformation characteristics of the concrete. A total of 140 specimens were tested under constant amplitude loading. Based on the fatigue strength results, empirical ex-pressions between the stress level (S), number of cycles (N) and probability of failure (P), S-N-P relationships, were derived. Using deformation characteristic results, an empirical expression for the total longitudinal strain (&maX) as a function of the cycle ratio (N/NF) and the loading time (t) was derived. This expression can be used to predict the fatigue life from deforma-tions early in the life. A total of 180 specimens were tested under various variable load histories of a given statistical distribution. The effect of both small and large amplitudes on fatigue strength and deforma-tion characteristics was examined. Based on fatigue strength results, the validity and limitations of the Palmgren-Miner hypothesis were examined. The PM hypothe-sis was found to give more or less unsafe predictions of the fatigue life depending on the load histories. Features of the loading histories affecting the accuracy of the hypothesis are discussed and an empirical relationship between loading histogram parameters and the Miner-sum at failure is presented. The empirical expression for the total longitudinal strain de-rived for constant amplitude tests is modified for tests under variable load histories.

DOI:

10.14359/6402


Document: 

SP75-15

Date: 

September 1, 1982

Author(s):

H. Roper and G. B. Hetherington

Publication:

Symposium Papers

Volume:

75

Abstract:

Fifty concrete beams reinforced with 24 mm deformed bars in the tension zone, were subjected to sinusoidal load fluctuations at 6.7 Hz in air, 3 percent sodium chloride solution and natural sea water. Total numbers of cycles at failure varied between 10' and lo7 for calculated stress ranges in the steel between 100 MPa and 280 MPa. Two types of tension reinforcement were compared; one was a hot-rolled 230 Grade deformed bar, and the second a cold.-worked 410 MPa Grade deformed similar chemical composition. bar with a As practised in some countries, cold-working by twisting was found to reduce the fatigue endurance of the deformed reinforcement in concrete beams tested both in air and sea water. The detrimental effect of sea water or sodium chloride solution gaining access, via concrete cracks, to bars subjected to fatigue loading was confirmed. In sea water the influence of cyclic loading on the hot-rolled series was different to that on the cold-worked series; for the latter series a decrease in slope of portion of the S-N curve was observed, which may represent a fatigue limit within lo7 cycles, whereas for the former no such change in slope exists. A reduction of fatigue endurance was observed for tests in a 3 percent sodium chloride solution compared with data for beams loaded in natural sea water. when A fractographic investigation was conducted on typical failure surfaces of bars subjected to tests in concrete,in air, and in sea water.

DOI:

10.14359/6413


Document: 

SP75

Date: 

September 1, 1982

Author(s):

Editor: S.P. Shah

Publication:

Symposium Papers

Volume:

75

Abstract:

SP-75 The eighteen papers included in this volume report on international research into the fatigue of concrete structures. Among the topics are fatigue in structures subject to cyclic loading in offshore and Arctic environments; hydraulic fracturing effects of water; marine corrosion and fatigue strength; the validity of Miner's hypothesis; and methods of predicting crack widths and fatigue loading.

DOI:

10.14359/14127


Document: 

SP75-14

Date: 

September 1, 1982

Author(s):

Harvey Haynes and M. B. Balachandra

Publication:

Symposium Papers

Volume:

75

Abstract:

Nine fiber-reinforced-concrete spheres were subjected to external pressure loading; four spheres were tested to failure by static loading, and five by low-cycle fatigue loading. The state of stress in the wall of the spheres was multiaxial, varying from biaxial on the inside surface to triaxial elsewhere. The average triaxial state of stress was 0 1 = a2 and 0 3 = 0.3 CT . 1 The fatigue data show a substantial difference in behavior compared to that of previous work on confined concrete. Changing the stress levels, c 9 from 0.70 to 0.50 changed the cycles to failure from 10 to 346, respectively. However, a better parameter to describe fatigue behavior was the stress-to-strength ratio, (qcyc/f;' which varied from 1.55 to 1.08, respectively. Under triaxial compression, it appeared that cyclic loading in which all principal stresses cycle was a considerably more severe condition than cyclic loading in which only one principal stress cycles while the other two principal stresses remain constant.

DOI:

10.14359/6412


Document: 

SP75-13

Date: 

September 1, 1982

Author(s):

Kent Gylltoft, Krister Cederwall, Lennart Elfgren, and larsgunnar Nilsson

Publication:

Symposium Papers

Volume:

75

Abstract:

Bond-slip failure between a smooth steel bar and con-crete was studied in micro scale. Both theoretical and experimen-tal work are presented. The theoretical analysis was perfomed as a nonlinear fi-nite element analysis, based on fracture mechanics. Roth a virgin loading stageanda subsquentloadingstagewasmdelled. In the experimental part a total of ten pull-out tests were performed, both with monotonic loading and cyclic loading. As far as the load-slip relations are concerned, the specimens were much softer at virgin loading compared to subsequent repeated loading. This is suggested to be caused by the phencmenon that the concrete, when it was cast, did not completely grow into the irregularities of the steel. The gaps, which consequently arised, were determined to be of the same magnitude as the depth of the irregularities, and were causing a soft performance for shear movements at virgin loading. This softness also caused the shear stresses in the contact zone to be quite uniformly distributed along the anchorage length. At subsequent repeated loading, as far as shear movment in the same directionas the virgin loading is concerned, all gaps were filled up, which resulted in a much stiffer performance.

DOI:

10.14359/6411


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